Building Reliable Event-Driven Systems: Event Schemas, Versioning, Contract Testing and Events vs Commands (part-4)

Short summary

A detailed guide on contract testing for event-driven systems, explaining why integration tests alone can't protect unknown consumers from schema changes. It covers consumer-driven contracts, where consumers declare their expectations and producers verify compliance. Practical examples show how field renames or constraint changes can silently break downstream services at runtime.

• •Contract testing catches schema changes that break unknown consumers before production
• •Consumer-driven contracts let consumers declare expectations rather than adapting to producer definitions
• •Contracts should capture constraints and meaning, not just field names

Generated with AI, which can make mistakes.